# Notes 

## TODO:

- Web Server
  - Async servlet
  - Reactive servlet
- Zuul
- Web Clients
  - Reactive WebClient
  - Feign
- Hystrix
- Messaging
- Reactor
- RxJava

Discuss what do we do with the `TraceKeys` in callables / runnables
  
## Done:

- Web Server
  - Simple handler interceptor
- Web Clients
  - RestTemplate
- Slf4j
  - with Brave in place it will also work for any other implementation (e.g. log4j)
- Async
  - Runnable / Callable
  - TraceExecutors etc.
  - @Async
- Scheduling

## Removed features

- `SpanLogger`
  - Name pattern of Span Logger will not be applicable
- `Sampler`
  - TODO: describe the new sampling mechanism
- `Metric` 
  - TODO: discuss what happens to `SpanMetricReporter` - is anybody actually using it?

# Migrations

## Core

With Brave instrumentation there are 2 different lifecycles. 

- Span creation and stopping and span reporting. 
- Span hooking to current context

When `brave.Span.finish()` is called the span gets stopped and reported.
In order to hook in the span to current context you need to call the try-with-resources clause via `withSpanInScope` `try (Tracer.SpanInScope ws = this.tracing.tracer().withSpanInScope(this.span.start())) { // do sth with the span } finally { this.span.finish(); }`

### Sleuth's Tracer to brave.Tracing

Before

```
import org.springframework.cloud.sleuth.Tracer;

Tracer tracer;
```

After

```
import brave.Tracing;

Tracing tracing;
```

### Child span creation

Before

```
Span child = tracer.createSpan("name");
```

After

```
// tracing is brave.Tracing injected instead of Sleuth's Tracer
brave.Span span = tracing.tracer().nextSpan().name("name");
```

### Span closing

Before

```
Span child = tracer.createSpan("name");
try {
  // do sth
} finally {
  tracer.close(child);
}
```

After

```
// tracing is brave.Tracing injected instead of Sleuth's Tracer
brave.Span span = this.tracing.tracer().nextSpan().name("name");
try {
  // do sth
} finally {
  span.finish();
}
```

### Span tagging

Before

```
tracer.addTag("foo", "bar");
```

After

```
// tracing is brave.Tracing injected instead of Sleuth's Tracer
this.tracing.tracer().currentSpan().tag("foo", "bar");
```

## `ArayListSpanAccumulator` renamed to `ArrayListSpanReporter`

Before

```
org.springframework.cloud.sleuth.util.ArrayListSpanAccumulator
```

After

```
org.springframework.cloud.sleuth.util.ArrayListSpanReporter
```

## Percentage -> Probability

`org.springframework.cloud.brave.sampler.SamplerProperties#percentage` renamed to `org.springframework.cloud.brave.sampler.SamplerProperties#probability`

and 

`org.springframework.cloud.sleuth.sampler.PercentageBasedSampler` renamed to `org.springframework.cloud.sleuth.sampler.ProbabilityBasedSampler`

Related to https://github.com/spring-cloud/spring-cloud-sleuth/issues/397

## Async

### `TraceRunnable` and `TraceCallable` moved to `instrument.async`

Before

```
org.springframework.cloud.sleuth.TraceRunnable
org.springframework.cloud.sleuth.TraceCallable
```

After

```
org.springframework.cloud.sleuth.instrument.async.TraceRunnable
org.springframework.cloud.sleuth.instrument.async.TraceCallable
```

### `TraceableExecutorService` has the constructor with `BeanFactory` remaining

Before

```
public TraceableExecutorService(final ExecutorService delegate, final Tracer tracer,
			TraceKeys traceKeys, SpanNamer spanNamer) {
    //...
	}

	public TraceableExecutorService(BeanFactory beanFactory, final ExecutorService delegate) {
    //...
	}

	public TraceableExecutorService(final ExecutorService delegate, final Tracer tracer,
			TraceKeys traceKeys, SpanNamer spanNamer, String spanName) {
		//...
	}
  ```

After

```
public TraceableExecutorService(BeanFactory beanFactory, final ExecutorService delegate) {
		//...
	}
	

public TraceableExecutorService(BeanFactory beanFactory, final ExecutorService delegate, String spanName) {
		//...
	}
```

### `TraceableScheduledExecutorService` changed constructor

Before

```
public TraceableScheduledExecutorService(ScheduledExecutorService delegate,
			Tracer tracer, TraceKeys traceKeys, SpanNamer spanNamer) {
		super(delegate, tracer, traceKeys, spanNamer);
	}
```

After

```
public TraceableScheduledExecutorService(BeanFactory beanFactory, final ExecutorService delegate) {
		super(beanFactory, delegate);
	}
```

### `TraceAsyncAspect` changed constructor

Before

```
@Deprecated
	public TraceAsyncAspect(Tracer tracer, TraceKeys traceKeys, BeanFactory beanFactory) {
		this.tracer = tracer;
		this.traceKeys = traceKeys;
		this.beanFactory = beanFactory;
	}

	public TraceAsyncAspect(Tracer tracer, TraceKeys traceKeys, SpanNamer spanNamer) {
		this.tracer = tracer;
		this.traceKeys = traceKeys;
		this.spanNamer = spanNamer;
		this.beanFactory = null;
	}
```

After

```
public TraceAsyncAspect(Tracing tracing, SpanNamer spanNamer, TraceKeys traceKeys) {
		//
	}
```